Material delivery system

ABSTRACT

A delivery system for hot asphalt includes a plurality of semitrailers. Each trailer includes a V-shaped hopper having an asphalt supporting beam extending longitudinally through it. A tube extends around the hopper for use in spraying lubricating oil into the hopper prior to the loading of asphalt. Each trailer further includes a conveyor for unloading asphalt from the hopper into a paving machine. The conveyor is driven by a hydraulic motor that is controlled by a valve. The valve is mounted in the trailer for activation by a prod mounted on the paving machine so that the operation of the conveyor is controlled from the paving machine.

United States Patent 1191- Holland 1 MATERIAL DELIVERY SYSTEM [75] Inventor: John H. Holland, Norman, Okla.

[73] Assignee: ArkansasRockland Gravel Co.,

Murfreeshow, Ark.

221 P1166; 06.6, 1971 21 Appl. N65; 187,185

Related US, Application Data [62] Division of Ser. No. 852,345, Aug. 22, 1969, Pat. No.

52 u.s.c1 214/52, 222/178, 222/564 51 116.0 ..B60p1/38 [58] Field of Search.... 198/57, 58; 214/8318, 83.2, 214/8334, 83,36,'5l9,:17 D, 152; 222/415, 1 178, 564; 298/35 1/1927 Napier 404/101 Jan. 29, 1974 FOREIGN PATENTS OR APPLICATIONS 1,024,364 3/1966 Great Britain 214/83.36

Primary Examiner-Gerald M. Forlenza Assistant ExaminerFrank E. Werner Attorney, Agent, or Firm-D. Carl Richards et a1.

[57 ABSTRACT A delivery system for hot asphalt includes a plurality of semi-trailers. Each trailer includes a V-shaped hopper having an asphalt supporting beam" extending longitudinally through it. A tube extends around the hopper for use in spraying lubricating oil into the hopper prior to the loading of asphalt. Each trailer further includes a conveyor for unloading asphalt from the hopper into a paving machine. The conveyor is driven by a hydraulic motor that is controlled by a valve. The valve is mounted in the trailer for activation by a prod mounted on the paving machine so that the operation of the conveyor is controlled from the paving machine.

2 Claims, 9 Drawing Figures PAIENI JAmIQM SHEET l U? 4 Ill FIG. I

FIG. 2

PAIENIE JAN 2 9 I974 SHEET 2 [IF 4 PATENTED JAN 2 9 I974 sum 3 [1F 4 FIG. 6

FIG. 7

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SHEET I; (If 4 v 1 MATERIAL DELIVERY SYSTEM This is a divisional application of application Ser. No. 852,345, filed Aug. 22, 1969, by John H. Hollandentitled MATERIAL DELIVERY SYSTEM, now-US. Pat. No. 3,647,096.

BACKGROUND or THE INVENTION In the paving industry, hot asphalt is commonly transported to paving sites in dump trucks. The trucks receive hot asphalt from an asphalt mechanism located at an asphalt plant and deliver it to paving machines located at the paving sites. Modern paving machines have the ability to lay down hot asphalt very rapidly. Because of this, large number of dump trucks is required to keep a paving machine supplied with asphalt, especially whenthe machine is located at apaving site remote from the asphalt plant.

As the number of trucks employed to transport hot asphalt to paving machines increases, a number of problems arise. For example, delays caused by traffic problems and the like are magnified when a large number-of trucks is involved. Also, the logistics of truck maintenance increase greatly. Finally, it is more difficult to'keep track of and control over a large number of trucks. Thus, it is highly desirable to reduce the number of trucks employed in an asphalt supply operation.

Heretofore, attempts to reduce the number of trucks required to'supply asphalt to paving machines have centered around the designanduse of large capacity dump trucks for transporting hot asphalt. Large capacity-dump trucks have not-gained wide acceptance for use in transporting asphalt because the use of such trucks results in'seve'ral problems. For example, asphalt .supply"trucks must be operated insuch a manner as to feed the asphalt gradually into the paving machines. When dump trucks are used to supply asphalt, this is accomplished by slowly raising the bed'of the truck as the truck movesforward ahead of the paving machine. During'suc'h a process, if the dump truck and the paving machine become separated, asphalt is dumped onto the ground ahead of the paving machine. In such an event, the asphalt mustbe'shoveled away from the path of the paving machine before more asphalt can be laid down. Obviously, the larger the capacity of the dump truck, the greater the shoveling problem is whenever a separation occurs. j

Another problem that results from the use of .large capacity dump trucks involves the tendency of asphalt to form into clumps or batches. These clumps tend to remain in the bed of a dump truck as it is raised and to then fall suddenly through the rear of the truck into the paving machine that is receiving ashpalt from the truck. When this occurs the paving machine forms waves or ridges in the pavement being laid down. Also, when large clumps fall from a'dump truck, the truck often becomes dan gerously unbalanced.

Yet another problem that-arises from the use of large dumptrucks relates to overhead obstructions such as wires, trees, viaducts, etc. Asphalt cannot be delivered to a paving machinefrom a dump truck except by raising the bed'of the truck. When an overhead obstruction prevents the raising of the bed, other means for delivering asphalt to the paving machine must be found.

Avery critical problem involving the use of large'capacity dump trucksto transport results from the tendency of asphalt to flow from the rear or bottom of a dumpbed first and to remain in the front or top of the bed as the bed is raised. Most large capacity dump trucks have a relatively long dump bed. The presence of asphalt in the front or top of a long dump bed as the bed is raised results in a very marked tendency of the truck to tip over. This problem is so acute that large capacity dump trucks are seldom used to transport asphalt to paving sites having any appreciable slant or bank.

The copending application of Robert D. Plant filed of even date herewith relates to a material delivery system in which hot asphalt is transported to paving machines in large capacity semi-trailers. Each trailer is provided with a conveyor system for moving the asphalt from the trailer to a paving machine. The trailers are not dumped, and, accordingly, the problems of asphalt of clumping and truck overturning experienced in the use of large capacity dump trucks are eliminated. Operation of the trailers is' controlled from the paving machines that receive the asphalt. This assures both delivery of the asphalt at the proper rate and immediate termination of delivery upon separation of the trailer and paving machine.

This invention comprises an. improvement over the material delivery system disclosed in the aboveidentified application of Robert D. Plant. In the improved version of the system, the movement of asphalt out of the trailers is facilitated by spraying the trailers with lubricating oil before they are loaded with asphalt. An asphalt supporting beam is positioned above and parallel to the conveyor of each trailer. The beam prevents excessive asphalt packing in the trailer without hindering the unloading of asphalt.

The improved version of thesystem is further characterized in that the operation of the conveyor of each trailer is controlled by a valve mounted on the trailer. The valves are positioned on the trailers for actuation by prods mounted on the paving machines. This permits both control of the unloading of the trailers from the paving machines and the unloading of the trailers in situations where no prod is available.

SUMMARY OF THE INVENTION In accordance with the preferred'embodiment, this invention comprises a plurality of vehicles each for transporting material from a delivery device to a receiving device and each including an unloading mechanism for despensing material to-the receiving device. Each vehicle includes an unloading mechanism control system that is mounted for actuation from the receiving device. Preferably, the unloading mechanism of each vehicle includes a conveyor and a material supporting beam that extends parallel to the conveyor.

DESCRIPTION OF THE DRAWINGS A more complete understanding of the invention may be had be referring to the following Detailed Description when taken in conjunction with the drawings, wherein:

FIG. 1 is a side view of a portion of a material delivery system employing the invention;

FIG. 2 is a back view of a'semi-trailer employed in the system shown in FIG. 1;

FIG. 3 is a top view of a trailer shown in FIG. 2 in which certain parts have been broken away;

FIG. 4 is a side view of the trailer shown in FIG. 2 in which certain parts have been broken away and certain other parts have been illustrated schematically;

FIG. 5 is partial perspective view illustrating the left rear of the trailer shown in FIG. 2;

FIG. 6 is a view similar to FIG. 5 illustrating the right rear of the trailer;

FIG. 7 is a transverse sectional view of the trailer shown in FIG. 2;

FIG. 8 is enlarged view similar to FIG. 1 which illustrates the operation of the system, and

FIG. 9 is a schematic illustration of hydraulic circuitry employed in the system.

DETAILED DESCRIPTION Referring now to the drawings, like reference numerals designate like parts throughout the several views. Referring particularly to FIG. 1, there is shown a material delivery system '10 employing the invention. The delivery system 10 includes a plurality of semi-trailers 12 (only one of which is shown) each adapted for a connection to and transportation by a conventional tractor 14. Each of the trailers 12 includes a hopper assembly 16 and an unloading assembly 18.

The trailers 12 of the system 10 receive hot asphalt from an asphalt mixing mechanism located at an asphalt plant (not shown) and deliver the hot asphalt to a paving machine 20 located at a paving site. The paving machine 20 supplied by the trailers 12 is conventional except that it is equipped with a prod 22 that is employed in controlling the unloading assemblies 18 of the trailers 12.

Referring now to FIGS. 2 through 8 and particularly to FIGS. 3,4 and 7 the structural detail of the trailers 12 of the system 10 are shown. The main structural elements of each trailer 12 are a pair of main beams 24 which extend the length of the trailer 12. A plurality of support beams 26 extend upwardly and outwardly from each of the beams 24. A top beam 28 extends along each side of the trailer 12 and is connected to the tops of thebeams 26. A pair of end beams 30 extend between the ends of the top beams 28 and two pairs of slantingbeams 32 extend from the main beam 24 to the top beam 28 at the front and at the rear of the trailer 12.

The main beams 24 of each trailer 12 are supported on a pair of conventional wheel and axle assemblies 34. A pair of fenders 36 extend outwardly from the main beams 24 over the wheels of the wheel and axle assemblies 34. At the front end of each trailer 12, a gooseneck assembly 38 including a conventional fifth wheel 40 is provided for attaching the trailer 12 to a conventional tractor 14. A pair of conventional support jacks 42 extend downwardly from the main beam 24 for supporting the trailer 12 whenever it is not connected to a tractor 14. l

The details of the hopper assemblies 16 of the trailers 12 are also illustrated in FIGS. 3, 4 and 7. Each hopper assembly 16 includes a floor 44 which is supported below the main beams 24 of the trailer 12 by a pair of sub-frame assemblies 46. A pair of side walls 48 slope upwardly and outwardly with respect to the floor 44 and are supported on the main beams 24 and the top beams 28. The walls 48 each extend at an angle of approximately 60 with respect to the floor 44.

'Each hopper 16 further includes a sloping front wall 52 extending between the main beams 24 and the end beam 30 at the front of the trailer 12. As is best shown in FIG. 4, the front wall 52 is reinforced by a plate 54 which extends vertically between the main beams 24 and the end beam 30 and a plate 56 which extends horizontally between the main beams 24. A rubber sealing member 58 extends from the front wall 52 to the floor 44.

An asphalt supporting beam 60 extends along the axial center of the trailer 12. The beam 60 is triangular in shape and extends the entire length of the hopper 16. The front end of the beam 60 is supported by a pair of triangularly shaped plates 62 that are fixed to the front wall 52 and to the beam 60. The rear end of the beam 60 is supported by a pair of plates 64 that are fixed to the end beam 30 at the rear of the trailer 12 and to the beam 60. The center of the beam 60 is supported by a pair of support assemblies 66. As is best shown in FIG. 7, each assembly 66 includes a beam 68 that extends between the top beams 28 of the trailer and a pair of flat bars 70 which extend angularly downwardly from the beam 68 to the beam 60.

It should be understood that the hopper assembly illustrated in the drawings can be employed in many applications other than asphalt delivery trailers. For example, the hopper can be used in stationary applications such as coal bins, etc. Furthermore, the hopper can be employed as a part of various material delivery vehicles which need not be of the trailer variety.

Each trailer 12 of the delivery system 10 is provided with a system for lubricating the side walls 48 and the front wall 52 of the hopper 16 before asphalt is loaded into the hopper. As is best shown in FIG. 4, the lubricating system includes a tank 76 that is supported by a plate 78 which extends through the gooseneck assembly 38 parallel to the plate 56. A filler tube 80 extends from the tank 76 through a plate 82 that is mounted between the slanting beams 32 at the front of the trailer 12.

The filler tube 80 is provided with a removable cap 84. The cap 84 includes an air valve of the type commonly employed in automobile tires. In use. the cap 84 is removed and a suitable lubricating fluid is pumped into the tank 76. The cap 84 is then replaced and compressed air is directed through the air valve in the cap to pressurize the interior of the tank 76.

A tube 86 extends from the tank 76 to a valve 88 having a control handle that extends through the plate 82. The outlet of the valve 88 is connected to a square tube 90 that extends around theside walls 48 and the front walls 52 of the trailer 12. The tube 90 has holes formed through it at spaced points along its bottom side. Therefore, whenever the valve 88 is opened, lubricating fluid from the tank 76 is sprayed on to the side walls 48 and the front wall 52 through the holes in the tube 90.

Of course, any lubricating fluid can be employed in the lubricating system. It has been found that diesel fuel works very well as a hopper lubricant. Since this material is readily available and very inexpensive, its use is preferred.

FIGS. 2 through 7 illustrate the details of the unloading assemblies 18 of the trailers 12. As is best shown in FIG. 4, each unloading assembly 18 comprises a conveyor 94 which passes through the hopper l6 and out the rear end of the trailer 12. As is best shown in FIG. 3, the conveyor 94 comprises a plurality of evenly spaced bars 96 and a pair of chains 100 connected to the opposite ends of the bars 96. The chains 100 move the bars 96 through the hopper 16 from front to rear along a course extending just over the floor 44. From the hopper 16, the bars 96 pass under a gate 102 that is hingedly supported atthe rear of the trailer 12 and around a large diameter roller 104. From the roller 104, the chains 100 drive the bars 96 along a course extending under the hopper l6 and then under the sealing member 58 and into the front end of the hopper 16.

As is best shown in FIG. 4, the chains 100 each extend between a sprocket 106 positioned at the front of the trailer 12 and a sprocket 108 positioned at the rear of the trailer 12. As is shown in FIG. 7, the chains 100 are protected by a pairof channels 110 formed between the lower ends of the walls 48 and the floor 44 as they travel through the hopper 16. As the chains 100 pass under the hopper 16 on their return course, they are protected by a pair of flanges 112 extending from the sub-frames 46. The bars 96 of the conveyor 94 are purposely exposed during their travel along the return course so that any material from the hopper 16 which input of a speed reducer 132. The speed reducer 132 drives a jack shaft 134 that extends through the rear of the trailer to a sprocket 136 that is positionedin an extension 138 of the right side main beam 24. The

sprocket 136 drives'a chain 140 which in turn drives a sprocket 142v that-comprises the input of a shaft mounted speed reducer 144. The speed reducer 144 is mounted on a shaft 146 that extends across the back of the trailer'12. The shaft 146 supports and drives the sprockets 108 which in turn drive the chains 100. Thus, whenever hydraulic fluid is supplied to the motor 120, the motor rotates the shaft 146 through the speed reducer 132, the jack shaft 134 and the speed reducer 144. The shaft 146 in turn rotates the sprockets 108 which drive the conveyor 94. 7

Referring now to FIGS. 8 and 9, the hydraulic motor 120is operatedby a hydraulic system 150 that is entirely contained within the trailer 12. Thesystem 150 includes a control valve 152 which is secured to the bottom frame of the trailer. The valve 152 includes a rearwardly extending actuator that is coupled to a valve control pad 156 by a link 158. The pad 156 is pivotally supported on a'shaft 160 that extends between the main beams 24 of the trailer 12. The valve 152 is so arranged that it is closed when the pad 156 is in the position shownand is open when the pad 156 is pivoted toward the valve 152.

The hydraulic system 150 of the trailer 12 further includes apump 162 which forces hydraulic fluid from a tank 164 to the motor 120. A relief valve 166 and a pressure compensated flow control unit 168 are also included in the system 150. Thus, whenever the pad 1567is pivoted to open a valve 152, the pump 162 supplies hydraulic fluid to the motor 120 at a rate controlled by the flow control unit 188.

The control valve control pad arrangement of the system has utility in systems other than conveyor motor control systems. For example, such an arrangement could be used to control the brakes of delivery vehicles including dump trucks, and to thereby prevent separation of the vehicles and a paving machine or other receiving device, In such a case, operation of the control valve controls the flow of energizing fluid to the brakes of the vehicle.

The pad 156 of the trailer 12 is mounted for actuation by the prod 22 of the paving machine 20. The prod 22 is supported in the asphalt receiving portion of the paving machine by a pair of upwardly extending brackets 172. The prod 22 includes an outer cylinder 174 that is secured to the brackets 172 and a stinger 176 that is slidably supported in the outer cylinder 174. The stinger 176 is hollow and has a spring 178 positioned within it. A piston 180 extends into engagement with the spring 178 inside the stinger 176.

The piston 180 of the stinger is connected to a piston 182 which comprises a portion of a hydraulic cylinder 184. Whenever hydraulic fluid is directed into the blind end of the cylinder 184, the piston 182 of the cylinder is driven toward the front of the paving machine 20. The piston 182 forces the piston 180 toward the front of the paving machine which in turn operates through the spring 178 to drive the stringer 170 out of the outer cylinder 174 of the prod 22.

As is shown in FIG. 9, the cylinder 184 of the prod 22 is operated by a hydraulic control system 186 mounted on the paving machine 20. The system 186 includes a pump 188 which draws a hydraulic fluid from a tank 190. The pump supplies fluid to a control valve 192 which controls the flow of fluid to and from the rod and blind ends of the cylinder 184. Thus, by operating the valve 192, the stinger 176 of the prod 22 can be either extended, withdrawn or maintained in any desired position.

When the stinger 176 of the prod 22 is withdrawn, its distal end is positioned about one inch from the valve control pads 156 of trailers 12 that are backed into engagement with the paving machine 20'. Whenever a trailer is properly positioned for unloading into the paving machine 20, the valve 192 of the hydraulic system 186 is actuated to extend the stinger 176 of the prod 22. As the stinger 176 moves out of the cylinder 174, it pivots the pad 156 of the trailer toward the valve 152. This action opens the valve 152 to permit hydraulic fluid to flow to the motor 120. The motor thereupon drives the loading assembly 18 of the trailer 12 to unload asphalt from the trailer into the paving machine. The cylinder 184 and the spring 178 are designed to apply a contact pressure of about 200 pounds between the stinger 176 of the prod 22 and the pad 156 of the trailer 12. This prevents accidental closings of the valve 152 during an unloading operation.

Referring to FIG. 2, a lever 194 is secured to a shaft 196. The shaft 196 is pivotally supported in a tube 198 that is secured to the extension 124 of the left main beam 24 of the trailer 12. The shaft 196 extends to a cam 200 positioned for engagement with the pad 156 of the trailer. Thus, by operating the lever 194, the pad 156 may be pivoted to open the valve 152. This feature is useful whenever it is desired to unload the trailer other than into a paving. machine. The lever may also be employed to control the unloading of a trailer 12 into a paving machine that is not equipped into a prod 22. Thus, by simply extending a rope from the lever 194 to the operator of the paving machine, the unloadrelative to the paving machine.

ing of the trailer can be controlled from any paving machine.

It should be understood that the hydraulically actuated prod 22 illustrated in FIGS. 8 and 9 is exemplatory only and that many other structures may be employed to operate the valve control pads 156 of the trailers 12 and to thereby control and unloading of the trailers 12 from the lay down machine. For example, the paving machine can be equipped with a fixed rod having a. first spring loaded tip. Alternatively, an electrical system including a motor and lead screw arrangement can be employed. Finally, a mechanical pad pivoting structure comprising a-pad engaging rod and a suitable lever system for advancing and retracting the rod can be employed. All that is required is to equip the paving machine with some mechanism for pivoting the pad 156 when a trailer 12 is properly positioned in use, the material delivery syst4m l transports hot asphalt from an asphalt mixing mechanism located at an asphalt plant to a paving machine located at a paving site in one or more semi-trailers 12. The hopper 16 of each trailer 12 is lubricated prior to receivng asphalt from the asphalt mixing mechanism. This is accomplished by removing the cap 84 from the filler tube 80 and then pumping diesel oil into the tank 76. When the tank isfull, the cap 84 is replaced and the tank 76 is pressurized with compressed air. The valve 88 is then opened to permit diesel oil from the tank 76 to flow through the tube 90 and onto the side walls 48 and the front wall 50 of the hopper 16.

When the lubrication of the trailer has been completed, hot asphalt is loaded into the trailer from the asphalt mixing mechanism. When the loading of the trailer 12 has been completed, the trailer is transported to the paving site by a tractor 14. At the paving site, the tractor 14 is operated to back the trailer 12 into engagement with the paving machine 20.

When the trailer 12 is properly positoned relative to the paving machine 20, the operator of the paving machine manipulates the control valve 192 of the hydraulic control system 186 on the paving machine to direct hydraulic fluid from the pump 188 to the blind end of the hydraulic cylinder 184. This action drives the stinger 176 out of the cylinder 174 of the prod 22. The stinger 176 pivots the valve control pad '156 on the trailer 12 to open the valve 152 of the hydraulic control system 150 of the trailer.

As soon as the valve 152 is open, the hydraulic system 150 supplies hydraulic fluid to the motor 120. The motor 120 in turn operates the conveyer 94 of the trailer 12 to unload asphalt from the hopper 16 into the paving machine 20. Of course, when the trailer 12 is employed to deliver asphalt to paving machines equipped with a fixed prod. the control pad 156 is pivoted to open the valve 152 as the trailer 12 is backed into engagement with the paving machine 20. In either case, should a separation between the trailer 12 and the paving machine 20 occur, disengagement of the prod on the paving machine from the pad 156 allows the pad to return to its normal position, whereupon the valve 152 of the trailer is closed. This action immediately terminates the unloading of asphalt from the trailer 12.

The operation of the unloading assembly 18 of the trailer 12 is facilitated by the beam 60 of the hopper 16. The beam 60 supports the contents of the hopper l6 and thereby lessens the load on the conveyor 94. As will be noted from FIG. 7, a vertical column of material is disposed on each side of the baffle or beam 60. The amount of support provided depends upon the tendency of the material in the hopper 16 to bridge between the beam 60 and the walls 48. Asphalt exhibits a very marked tendency to bridge and, accordingly, the beam 60 greatly reduces the amount of power required to unload asphalt from the trailer 12.

During the operation of the trailer 12 illustrated in the drawings, an interesting phenomenon has been observed. it appears that the amount of asphalt unloaded by the trailer is directly related to the height of the asphalt supporting beam 60 relative to the floor 44. Thus, if the conveyor 94 is operated at a uniform speed and the beam 60 is raised relative to the floor 44, more asphalt is unloaded. Conversely, if the beam is lowered relative to thefloor 44, less asphalt is unloaded. Thus, the rate at which asphalt is unloaded from the trailer may be controlled in two ways. First, the flow control unit 168 of the hydraulic system of the trailer adjusted to control the rate of flow of hydraulic fluid to the motor 120. This controls the speed of operation of the conveyor 94. Second, the height of the beam 60 relative to the floor 44 may-be adjusted. This controls the amount of asphalt that is unloaded by the conveyor during each incremental unit of conveyor travel. The height of the beam 60 relative to the floor 44 also directly effects the amount of power required to unload asphalt from the trailer.

The phenomenon which results in the controlled delivery of material is not fully understood. However, it will be noted from FIG. 7 that the beam 60 is substantially narrower than the conveyor system 94. This leaves at least two significant vertical columns of material which would appear to rest directly upon the con.- veyor. The bridging effects observed in the material are undoubtedly produced by horizontal pressures established in the vertical columns of material by the beam 60. These horizontal pressures are produced by the reduction in the cross-section of the hopper caused by the beam, and are enhanced by the sloping surfaces of the beam 60 which face the sloping side walls 48 of the hopper. The compaction resulting from road vibrations enhances these pressures. Immediately below the beam 60, the increased cross-sectional width of the hopper undoubtedly produces a layer of material having substantially lower horizontal pressures which prevent significant bridging. This apparently results in a horizontal, preferential shear zone in the vicinity of the beam 60 which permits the conveyor to more easily shear the material along a substantial length of the hopper. Since the hopper has no rear wall, material is freely delivered at a height corresponding to the height of the baffle 60 throughout the delivery period. Thus,

the rate of delivery is almost entirely related to the speed of the conveyor from the start of the delivery of the material until all material has been delivered.

When the unloading of the trailer 12 has been completed, the operator of the paving machine 20 manipulates the control valve of the hydraulic control system 186 on the paving machine 20 to withdraw the stinger 176 of the prod 22 into the cylinder 174. This permits the valve control pad 156 to return to its normal position, whereupon the valve 152 terminated the operation of the unloading assembly 18 of the trailer by discontinuing the flow of hydraulic fluid to the motor 120. In material delivery systems including paving machines equipped with fixed prods, this function is accomplished by simply driving the unloaded trailer away from the paving machine. In either case, the unloaded trailer is then' returned to the asphalt plant by the tractor l4, whereupon it is relubricated and filled with another, second'load of asphalt.

ln should be understood that the trailers 12 of the delivery system can be employed to deliver many materials in addition to hot asphalt. For example, the trailers 12 may be used to deliver sand and/or gravel to paving sites for use in forming a pavement base. In such a case, it normally is not necessary to lubricate the hoppers 16 of the trailers 12. Additonally, the trailers may be employed to transport raw aggregrate to an asphalt plant on return tripsfrom the paving site. In such a case, the trailers produce on both legs of the trip. Finally, the trailers may be used to transport and unload materials entirely unrelated to the paving industry.

The unloading system illustrated in the drawings is superior to prior delivery systems in several respects. For example, the use of the system does not involve the raising of a dump bed. Therefore, the trailers of the system do not tend to overturn, even when they are unloaded on a steep bank or grade. Further asphalt is unloaded by the system smoothly and evenly without tending to form. into clumps thatfall suddenlyinto a paving machine.

. Another advantage of the material system shown in the drawings over prior systems results fromthe use of the lubricating system and the asphalt supporting beam. These features of the system facilitate the unloading of asphalt from the trailers smoothly and evenly without placing an undue load on the unloading assemblies of the trailers.

A very important advantage inherent in the present material delivery system involved the controlling of the unloading assemblies of the system from the paving machine. This assures the immediate termination of the delivery of asphalt upon any separation between the trailers of the system and the paving machine. Thus, the problem of removing asphalt accidentally dumped in front of a paving machine which has plagued prior delivery systems is completely eleminated. 1

Yet another advantage of the material delivery sys-. tem disclosed'herein results from the positioning of the.

but is capable of rearrangement, modification and subillustrated in the drawings and described herein,in the foregoing specification, it will be understood that the invention is not limited to the embodiment disclosed stitution of parts and elements without departing from the spirit of the invention.

What is claimed is:

l. The method for transporting hot-mix asphalt and the like from a loading site to-a delivery site and delivering the material at the delivery site which comprises placing a predetermined quantity of the material in a bulk hopper at the loading site with the material constrained on two opposed sides by downwardly converging bin walls and with at least one of the other sides of delivered.

the material free-standing at the natural angle of repose of the material, transporting the bulk hopper from the loading site to the delivery site, and moving the material from the bottom of the quantity of material horizontally over the bottom of the hopper toward the side having the natural angle of repose while permitting the material to maintain its natural angle of reposeduring at least'the initial movement of the material to thereby prevent establishing any longitudinally extending shear planes in the material caused by any bin structure that would interfere with movement of the material at the free-standing surface of the material forming the natural angle of repose.

a vertical column of the material having horizontalpressures greater than the horizontal pressures in the underlying zone by causing a bridging action across the I vertical column of material and thereby establishing a preferential shear zone generally within the zone of decreased pressures, and moving the material from the portion of the vertical column below the preferential shear zone toward the edge of the material standing at the natural angle of repose without restraining move ment of the material below the zone of increased pressure until it is delivered from the hopper to cause the material to be delivered at a predetermined level cor responding substantially to the preferential shear zone, and controlling the linear rate at which the material is 

1. The method for transporting hot-mix asphalt and the like from a loading site to a delivery site and delivering the material at the delivery site which comprises placing a predetermined quantity of the material in a bulk hopper at the loading site with the material constrained on two opposed sides by downwardly converging bin walls and with at least one of the other sides of the material free-standing at the natural angle of repose of the material, transporting the bulk hopper from the loading site to the delivery site, and moving the material from the bottom of the quantity of material horizontally over the bottom of the hopper toward the side having the natural angle of repose while permitting the material to maintain its natural angle of repose during at least the initial movement of the material to thereby prevent establishing any longitudinally extending shear planes in the material caused by any bin structure that would interfere with movement of the material at the free-standing surface of the material forming the natural angle of repose.
 2. The method of claim 1 further characterized by establishing prior to arrival at the delivery site a zone in a vertical column of the material having horizontal pressures greater than the horizontal pressures in the underlying zone by causing a bridging action across the vertical column of material and thereby establishing a preferential shear zone generally within the zone of decreased pressures, and moving the material from the portion of the vertical column below the preferential shear zone toward the edge of the material standing at the natural angle of repose without restraining movement of the material below the zone of increased pressure until it is delivered from the hopper to cause the material to be delivered at a predetermined level corresponding substantially to the preferential shear zone, and controlling the linear rate at which the material is delivered. 